Snowmobiler Caleb Moore died this morning, a week after crashing his Snowmobile during the freestyle finals at the X Games in Aspen. Moore under-rotated on a backflip, and slammed his head into the ground as his snowmobile rolled over him. The 25-year-old was airlifted to the hospital, where he underwent surgery for bleeding around his heart. Later "brain complications" made his prognosis pessimistic.

We've worked closely on safety issues with athletes, course designers and other experts for each of the 18 years of X Games. Still, when the world's best compete at the highest level in any sport, risks remain.

Moore is the first athlete to die in the history of the X Games, though freestyle skier Sarah Burke died one year ago in training.